Push to talk (PTT) communication service is a half-duplex service which may achieve one-to-many communication, which is characterized in that when PTT User Equipment (UE) initiates a group call service, a voice message thereof can be transmitted to each member of a preset PTT group simultaneously, and the service may be established rapidly. Based on the above characteristics, the PTT communication system has been widely used in many industries and occasions of government agency, public security, energy and traffic, airport and seaport, industrial and mining enterprise, military and fair or the like.
The current PTT communication system is generally developed based on the second generation mobile communication technology, i.e., a Global System for Mobile Communications technology (GSM). With the maturity and commercial popularization of the mobile communication technology, the PTT communication system must be evolved into a system which adopts 3G or 4G communication technologies. The PTT communication system has been evolved into a new system. Meanwhile, various scientific research institutions also do research on technologies in which a PTT system is combined with a public system. When the PTT system is combined with the public network or a very large number of customers use the PTT system, the coverage area of the PTT system needs to be expanded, multiple PTT cells may be managed, and therefore the PTT user equipment may also be distributed in multiple cells. Both of the user equipment for speaking and the user equipment for listening in the PTT system will change the cells due to location moving. Thus, for the user equipment for speaking and the user equipment for listening in the PTT system, the PTT system needs to have a mobility management function.
The enhanced Multimedia Broadcast Multicast Service (eMBMS) introduced by the fourth generation mobile communication Long-Term Evolution (LTE) system applies to the user equipment with a video function, which receives a digital audio/video service in a form of broadcast/multicast through the PMCH. In view of the characteristics of the eMBMS service, the eMBMS service may be used to achieve a data transfer function of calling and listening users of the PTT group. One eMBMS service transmission and receiving process is used as one data transmission and receiving process of the calling and listening user of the group, while a Temporary Mobile Group Identity (TMGI) defined in a protocol may also be used as an identifier of the PTT group. The UE obtains a TMGI of a group to which the current UE belongs according to a group information update process. In an MBMS process, each UE may judge whether belong to the group according to the TMGI.
In the protocol of the related art, when the user who is receiving the eMBMS service moves, no implementation method is given to the user about how to keep the service continuity, in which the above user moving may include that: the UE in a Radio Resource Control Idle (RRC_IDLE) state performs cell reselection, or the UE in a Radio Resource Control Connected (RRC_CONNECTED) state performs cell handover. According to the protocol of the related art, if UE moving does not result in a change of a Multicast Broadcast Single Frequency Network (MBSFN) area, the service will keep the continuity automatically. However, if the target cell does not contain the MBSFN area where the UE is receiving the service in an original cell, the UE needs to read mib, sib1 and sib13 of the target cell, and then reads a PMCH resource of a group needed to be received by the user from a Multipoint Control Channel (MCCH) according to the configuration of sib13. For the slowly moving user, if a PBCH channel of the target cell has good enough quality, the UE can configure the PMCH resource of the current MBMS service/group call in the target cell rapidly, during which the signal quality of the PMCH of the original cell can also keep the service continuity. However, for the fast moving user, if the Physical Broadcast Channel (PBCH) channel of the target cell has bad quality, before the PMCH configuration of the target cell is read, the signal quality of the PMCH of the original cell will quickly reduce, thereby resulting in temporary voice interruption, and reducing the user experience due to the fact that the above defects are contrary to the characteristics of rapid and efficient service of the PTT communication system.